1. Field of the Invention
This invention generally relates to a bicycle crank assembly. More specifically, the present invention relates to a bicycle crank assembly mounted on a bicycle crank axle.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One component that has been extensively redesigned is the bicycle crank assembly.
The crank assembly is mounted on the crank axle of a bicycle. A conventional crank assembly has a crank axle mounting part non-rotatably mount on an end of the crank axle, a crank body extending from the crank axle mounting part in an outward in a radial direction, and a pedal mount provided at the tip of the crank body. In this type of crank assembly, a right side gear crank is conventionally known to be crimp-fastened to the crank axle (see, for example, Japanese Laid-Open Patent Publication No. 2004-249770).
A conventional left side crank assembly has a slit formed in the crank axle mounting part, and two clamping bolts are provided to narrow the slit with the crank axle with the slit gap prevented from turning by serrations on the left end of the crank axle. Furthermore, the left side crank assembly is fixed to the crank axle by a fixed bolt that screws into the left inner circumferential surface of the crank axle.
A bearing play adjustment function, such as bearing pressing, is not provided for the bearings of conventional crank axles. Therefore, adjustment of bearing play, that is, adjustment so that the crank axle rotates smoothly without bearing jounce in the axial direction, is accomplished by adjusting the degree of tightness when fixing the left side crank assembly with the fixed bolt. Then, when the bearing play adjustment is completed, the clamping bolt is tightened to narrow the slit and fix the crank assembly to the crank axle. Accordingly, since bearing adjustment is accomplished by the fixed bolt to fix the crank assembly in a conventional crank assembly, the play adjustment by the fixed bolt must be performed again when the crank assembly is removed from the crank axle and the crank assembly is mounted on the crank axle.
Conventionally, a crank assembly is fixed to the crank axle using a taper. When a taper is used for mounting and the fixed bolt that screws into the crank axle is not completely tightened, a gap is created between the crank assembly and the crank axle, such that the crank assembly can not be rigidly fixed to the crank axle. Therefore, a fixed bolt can not be used when adjusting the crank assembly for bearing play. When adjusting the crank assembly for bearing play in structures in which both components are coupled using a taper, it is necessary to adjust bearing play by inserting a shim into the gap between the bearing and the crank assembly.
However, when the bearing play is adjusted by the crank assembly and a taper is used to couple the crank assembly and the crank axle, however, bearing play must be adjusted each time the crank assembly is mounted. This adjustment is necessary because the position of the crank assembly in the axial direction is subject to shifting each time the assembly is removed due to the finish precision of the crank axle taper and the crank assembly taper. Thus, when the crank assembly shifts position in the axial direction, the bearing play must be adjusted to change the gap between the bearing and the crank assembly. In this case, the work of bearing adjustment becomes complicated since removing the fixed bolt and crank assembly must be repeated to add and subtract the shims when changing gap using shims during bearing play adjustment.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved bicycle crank assembly. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.